Method and apparatus for producing a three-dimensional object

ABSTRACT

A method for producing an object by layerwise solidification of the object by means of electromagnetic radiation is expedited by simultaneously solidifying the material of a layer at a plurality of places. 
     An apparatus for carrying out the method comprises an irradiation device (11, 12, 14, 15, 16) generating a plurality of beams (20, 21, 22) as well as a control device (7, 17, 18, 19) directing each of the plurality of beams independently to different regions of the layer (8a . . . 8d).

The invention relates to a method and an apparatus for producing athree-dimensional object.

Such a method or apparatus, resp., is known from document EP-A-0 171 069wherein the support is lowered within a bath of liquid resin which canbe polymerized, so as to form a layer of liquid resin, and this layer isthereafter polymerized or solidified, resp., at the points thereofcorresponding to the object by irradiation with a laser beam. Since thepolymerization requires a determined reaction time, the laser beam cannot be scanned across the layer at any speed whatsoever and theproduction time can therefore not be freely reduced.

It is the object of the invention to reduce the time required for theproduction of the object.

In the following the invention will be described with reference to anembodiment in connection with the figure which shows a partly sectionedschematic representation of an embodiment of the inventive apparatus.

A top open tank 1 is filled with a light-curable liquid resin material 3up to a level or surface 2. Within the tank 1 and the volume of theresin 3 there is a support 4 having a substantially plane and horizontalsupport plate 5 which is parallel to the surface 2 and may be displacedand positioned in direction perpendicular to the surface 2 and to thesupport plate 5, resp., by means of a schematically indicated elevationadjustment device 6. The elevation adjustment device is connected with acontrol device 7 for controlling the displacement position.

The object 8 which is formed by a plurality of layers 8a, 8b, 8c and 8din the manner described below is on the support plate.

An irradiation device 9 for solidifying the uppermost layer 8d adjacentto the surface 2 comprises an illumination device 10 having a radiationsource 11 which generates a focussed or directed beam 13 through a lensesystem 12. Preferably the radiation source 11 is a light source such asa laser, but may be any other source of electromagnetic radiation. Inthe region above the tank 1 or above the surface 2, resp., a pluralityof, for example three, mirrors 14, 15, 16 which are eachsemi-transparent are disposed one behind the other in direction of thebeam 13. The mirrors 14, 15, 16 are each independently mounted ongimbals and can be pivoted by means of schematically indicated drivingdevices 17, 18, 19 in such a manner that the beam 13 impinging on themirrors 14, 15, 16 can be positioned by the mirrors 14, 15, 16 asrespective independent reflected beams 20, 21, 22 within predeterminedregions of the surface 2. Alternatively also two rotating mirrors, arespective one for each coordinate direction, may be used inconventional manner.

The driving devices 17, 18, 19 are each connected with the controldevice 7 for controlling the direction of the beams 20, 21, 22.

In operation data about the shape of the object 8 as obtained by adesign program or the like are first stored within the control device 7.For producing the object 8 those data are processed so that the objectis decomposed into a large number of horizontal layers which are eachthin as compared to the object dimension and form data for each layerare provided.

For producing the first layer 8a the control device 7 controls theelevation adjustment device 6 to position the surface of the supportplate 5 to a predetermined elevation below the surface 2 correspondingto the thickness of the layer 8a. Hence, a liquid resin layer having athickness corresponding to the desired layer 8a exists between thesurface of the support plate 5 and the surface 2.

Thereafter the control device 7 controls the irradiation device 9 and inparticular the driving devices 17, 18, 19 so as to direct the beams 20,21, 22 reflected from each corresponding mirror 14, 15, 16 ontopredetermined regions of the layer 8a and to thereby solidify thoseregions. For example a boundary region of the first layer 8a can besolidified by a first beam 21 deflected by the intermediate mirror 15and the central region of the layer 8a can be solidified by the othertwo beams 20, 22. In this manner the boundary region is solidified alonga closed path which provides for an improved and in particular smootherstepless surface of the object. The inner region may then be solidifiedby the other beams 20, 22 in such a manner that those beams scanadjacent linear regions or each beam 20, 22 solidifies a separate regionor a separate field of the layer, resp. In the latter case it isadvantageous that the operative range of the mirrors 14 and 16 can besmaller or, with the same operative region of the mirrors, the size ofthe solidifiable layer is increased, resp. Anyway, it is important thata plurality of regions corresponding to the number of beams issimultaneously solidified owing to the simultaneous irradiation by meansof the beams 20, 21, 22 so that the layer 8a is produced in a shortertime in spite of the constant reaction time of the material.

After producing the first layer 8a the elevation adjustment device 6 islowered by the control device 7 by the amount of the intended thicknessof the second layer 8b so that a liquid layer having the thickness ofthe second layer 8b is formed on the first layer 8a. Thereafter thedriving devices 17, 18, 19 are controlled for solidifying the secondlayer in analogous manner as in the first layer. The following layers8c, 8d are produced in corresponding manner.

In place of the single radiation source 11 having a plurality of mirrors14, 15, 16 which is disadvantageous in that the light power of thereflected beams 20, 21, 22 is reduced corresponding to the number ofmirrors a plurality of radiation sources 11 each having an associatedmirror or deflection device, resp., for the light beam may be provided.It is a particularly advantageous modification of the describedapparatus to provide one radiation source and 5 mirrors whereby fourmirrors are annularly positioned around a fifth central mirror. Eachmirror is provided with a corresponding control or deflection device forthe respective light beam and is controlled by the control device 7 forsolidifying individual regions of the layers 8a . . . 8d. It isparticularly advantageous to control the central mirror so as to takeover the solidification of the boundary region of the layer as withmirror 15.

Rather than by using mirrors the brake-up of the beam 13 and theseparate deflection of the partial beams can also be obtained by aplurality of optical fibres whereby the beam 13 enters at one end of thefibres and the other end thereof is scanned across the surface by meansof a per se known x,y-positioning device in a manner corresponding tothe beams 20, 21, 22. A further possible modification is the use of aplastic, metal or plastic-coated metal or ceramic powder in place of theliquid resin. Any suitable methods such as dispensing or sprayingdevices, blades, drums, etc., may be used for applying a layer of thismaterial. The solidification of the material can also be made infunction of the characteristics thereof by other forms ofelectromagnetic radiation, such as cathode rays or heat radiation.

We claim:
 1. A method for producing an object by layerwisesolidification of a material which is solidifiable by electromagneticradiation, the method comprising the steps of(a) generating a layer ofsaid material, (b) producing a beam of electromagnetic radiation, (c)dividing said beam into a plurality of beams, (d) controllably directingeach one of said plurality of said beams independently onto apredetermined region of said layer, (e) solidifying said regions, and(f) repeating steps (a) to (e) until said object is formed.
 2. Themethod of claim 1,comprising using one of said plurality of beams forsolidifying a contour of said object and using the other of saidplurality of beams for solidifying an inner region of said layer whichis surrounded by said contour.
 3. An apparatus for producing an objectfrom a material which is solidifiable by electromagnetic radiation, theapparatus comprising:support means for said object, means for applying alayer of said material to said support means, irradiation means forproducing a plurality of beams of electromagnetic radiation, and controlmeans for independently directing each one of said plurality of beamsonto corresponding predetermined regions of said layer, wherein saidirradiation means comprises a single radiation source generating asingle beam and a plurality of semi-transparent mirrors which are eachcontrolled by said control means.
 4. The apparatus of claim 3,comprisingmeans for arranging said mirrors along the axis of said single beam. 5.The apparatus of claim 3,comprising five mirrors and means for arrangingsaid five mirrors such that a central mirror is surrounded by four outermirrors.